Industrial controllers are specialized computer systems used for the control of industrial processes or machinery, for example, in a factory environment. Generally, an industrial controller executes a stored control program that reads inputs from a variety of sensors associated with the controlled process or machine and, sensing the conditions of the process or machine, and based on those inputs and a stored control program, calculates a set of outputs used to control actuators controlling the process or machine.
Industrial controllers differ from conventional computers in a number of ways. Physically, they are constructed to be substantially more robust against shock and damage and to better resist external contaminants and extreme environmental conditions than conventional computers. The processors and operating systems are optimized for real-time control and are programmed with languages designed to permit rapid development of control programs tailored to a constantly varying set of machine control or process control applications.
Generally, industrial controllers have a highly modular architecture, for example, that allows different numbers and types of input and output modules to be used to connect the controller to the process or machinery to be controlled. This modularity is facilitated through the use of special “control networks” suitable for highly reliable and available real-time communication. Such control networks (for example, EtherNet/IP, DeviceNet and ControlNet) differ from standard communication networks (such as Ethernet) by guaranteeing maximum communication delays by pre-scheduling the communication capacity of the network, and/or providing redundant communication capabilities for high-availability.
As part of their enhanced modularity, industrial controllers may employ I/O modules or devices dedicated to a particular type of electrical signal and function, for example, detecting input AC or DC signals or controlling output AC or DC signals. Each of these I/O modules or devices may have a connector system allowing them to be installed in different combinations in a housing or rack along with other selected I/O modules or devices to match the demands of the particular application. Multiple or individual I/O modules or devices may be located at convenient control points near the controlled process or machine to communicate with a central industrial controller via the control network.
It is important to ensure highly reliable operation of industrial control systems. Such highly reliable operation may be important for ensuring the system consistently operates as expected, for example, in order to maximize functional safety, minimize costly downtime, and the like. An ongoing need therefore exists to ensure that industrial controllers and industrial control systems operate consistently with the highest reliability attainable.